## Issue Addressed
Cleaner resolution for #4006
## Proposed Changes
We are currently subscribing to core topics of new forks way before the actual fork since we had just a single `CORE_TOPICS` array. This PR separates the core topics for every fork and subscribes to only required topics based on the current fork.
Also adds logic for subscribing to the core topics of a new fork only 2 slots before the fork happens.
2 slots is to give enough time for the gossip meshes to form.
Currently doesn't add logic to remove topics from older forks in new forks. For e.g. in the coupled 4844 world, we had to remove the `BeaconBlock` topic in favour of `BeaconBlocksAndBlobsSidecar` at the 4844 fork. It should be easy enough to add though. Not adding it because I'm assuming that #4019 will get merged before this PR and we won't require any deletion logic. Happy to add it regardless though.
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